Organic solutions are used in various industries for washing, developing, or cleaning various substrates or materials and as a result, the organic solutions generally become contaminated with various polymeric materials that are dissolved in the organic solvents of which the organic solutions are composed.
For example, washout or developing processes are known for the preparation of flexographic printing plates, and the developing solutions become contaminated with various polymeric and non-polymeric materials from the non-imaged portions of the flexographic printing plate precursors. Such developing processes are described for example in U.S. Pat. No. 5,240,815 (Telser et al.), U.S. Pat. No. 7,226,709 (Kidnie et al.), and U.S. Pat. No. 7,279,254 (Zwadlo) and in U.S. Patent Application Publication 2005/0227182 (Ali et al.). Generally, the flexographic printing plate precursors are imaged and then developed to remove non-polymerized material while leaving the polymerized (cured) material intact to form a relief image in the resulting flexographic printing plates. Various organic solvents are generally contained in such developing solution including but not limited to, chlorinated hydrocarbons, saturated cyclic or acyclic hydrocarbons, aromatic hydrocarbons, lower aliphatic ketones, and terpene hydrocarbons.
Because flexographic printing plate precursors can be prepared from a variety of polymeric materials, it is usually necessary to match the imaged precursors with specific developing solutions so the non-polymerized materials can be quickly and completely removed to provide the relief images. Mechanical means such as brushing with rubbing means may be used to facilitate polymer removal.
The need for different developing solutions is a major inconvenience in the industry of flexography, particularly if all types of flexographic printing plate precursors are being imaged and processed in the same facility. The industry has been trying to develop effective and environmentally-friendly developing solutions to overcome these problems. For example, U.S. Pat. No. 6,248,502 (Eklund) describes the use of terpene esters in developing solutions to overcome some of these problems.
In addition, U.S. Pat. No. 7,326,353 (Hendrickson et al.) describes a useful process for purifying or recycling developing solutions containing specific organic solvents. This process requires the use of centrifuging the polymer-containing solvents with optional organic membrane filtration steps before or after centrifugation.